Pneumocystis carinii (P. carinii) is a major pathogen of patients with human immunodeficiency virus infection. The immune responses to P. carinii are poorly understood, but cytokines may play a role in both clearing P. carinii infection and in the hypoxia associated with P. carinii pneumonia (PCP) that may be exacerbated following initiation of therapy. We have completed a study with Dr. Vogel examining the effects of IL-12 in scid mice with PCP. In this model, no effect on PCP was seen when IL-12 was administered either at the time of exposure to P. carinii or 4 weeks after exposure. We have begun studies to examine the role of the major surface glycoprotein in inducing protective immune responses in mice. In the future, we plan to use the scid mouse model to further evaluate the role of individual cytokines in modulating P. carinii infection. It is hoped that these studies will provide insights into the role of cytokines in PCP, and may provide mechanisms for increasing clearance or decreasing the inflammation that may be causing hypoxia.